An exemplary thin and plane light-source employed in a liquid crystal display apparatus and the like is shown in FIG. 6(c). Specifically, a light guiding plate 213 is provided on a rear surface of a liquid crystal display member 212, and a surface-mount type light emitting apparatus 200 is provided on a side surface of the light guiding plate 213. In the plane light-source, the light guiding plate 213 and the light emitting apparatus 200 are placed, adjacent to each other, on a mounting surface 214 such that a side surface of the light guiding plate 213 and a light-outgoing surface 207a of the light emitting apparatus 200 are opposite to each other, thereby realizing a thin shape. Light is emitted from the light emitting apparatus 200, enters via the side surface of the light guiding plate 213, and then outgoes from an upper flat surface of the light guiding plate 213.
An exemplary light emitting apparatus 200 employed in the plane light-source is shown in FIGS. 6(a) and 6(b). Specifically, an LED chip (hereinafter, “chip”) is accommodated in a package member (hereinafter, “package”) that is in rectangular parallelepiped shape and includes a recess section. The light emitting apparatus 200 accommodates a chip 202, and includes a package 201 including a recess section having a reflector function to cause light to outgo to the outside. The recess section opens flatly with respect to a side surface of the light guiding plate 213. The reflector 203 (recess section) includes: a bottom surface on which the chip 202 is to be placed; and a tilted surface that is formed along a periphery of the bottom surface, such that light is emitted parallel to a mounting surface.
A substantially central part of the bottom surface of the recess section is a die-bond area that includes an electrode 204a on which the chip 202 is to be placed. A wire-bond area is provided in the vicinity of the die-bond area, and an electrode 204b is provided in the wire-bond area to supply the chip 202 with electric power. The chip 202 is placed in the die-bond area, connected to the electrode 204b via a wire 205, and sealed with a light-transmitting sealing resin 207 that contains a fluorescent material 206. When excited by light emitted from the chip 202, the fluorescent material 206 emits a light beam having a different waveform. The sealing resin 207 fills the recess section to the vicinity of a top surface of the recess section, thereby forming a light-outgoing surface 207a that is substantially flat, and protecting the chip 202 and the wire 205.
Known Document 1 (Japanese Unexamined Patent Publication No. 2003-249689 (published on Sep. 5, 2003)) teaches a light emitting apparatus that is similar in structure to the above-described light emitting apparatus. In the light emitting apparatus of Known Document 1, the chip is mounted to the die-bond area via a conductive layer, by flip chip bonding. Then, the fluorescent material is applied to the chip. Thereafter, the chip is sealed by a light-transmitting sealing resin. The light-transmitting sealing resin includes diffusion agents that are dispersed in the sealing resin. The diffusion agents reflect and scatter light that is emitted from the chip or the fluorescent material.
When the sealing resin fills the recess section to the vicinity of a top surface of the recess section and then is thermally cured, a smooth and parabolic concave surface is formed, with a deepest portion at its central section. This action is considered to occur because of the following. The thermal curing causes oil absorbency of the diffusion agent to increase, so that a part of components of the resin is absorbed by the diffusion agent. The diffusion agent absorbs the resin at an absorption rate that is higher than a ratio at which the volume of a diffusion layer increases as a consequence of the absorption of the resin. As a result, the volume of the diffusion layer decreases overall.
To increase a luminance of a plane light-source, it is necessary to increase a coupling efficiency, which is a ratio of (i) light that enters a side surface of the light guiding plate to (ii) light from the light emitting apparatus. For this reason, it is preferable to reduce a radiation angle, in a short-axis direction, of the package.
In the light emitting apparatus of Known Document 1, a slight concave surface is formed. This, however, occurs naturally as a result that the diffusion agent absorbs a part of component of the sealing resin during the thermal curing, and therefore does not contribute to improvement in the radiation angle, in a short-axis direction, of the package.